Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
danh voi » hanh voi, lanh voi, danh hoa
nam thuc » nam thuoc, am thuc, nam thu
thuc va » thuc vat, thuc dan, thuc day
hiem he » hiem xe, hieu he, thien he
sach ky » sac ky, sach y, sach ty
dai hoi » dai hoc, dai hai, dai moi
tai hoi » tai khoi, tai hai, tai hoe
he nam » ha nam, nghe nam

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ky nang ((tai hoi) or (dai hoi)). hiem he nam thuc va ((danh voi) OR (hanh vi)) hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky nang ((tai hoi) OR (dai hoi)). hiem he nam thuc va ((danh voi) OR (hanh vi)) hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky nang ((tai hoi) or (dai hoi)). hiem he nam thuc va ((danh voi) OR (hanh vi)) hoa viet".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky nang ((tai hoi) or (dai hoi)). hiem he nam thuc va ((danh voi) OR (hanh vi)) hoa viet*.